I have UCTD and have only recently realized my recent reduced (anosmia) and/or distorted sense of smell (parosmia) is probably due to a hitherto undiagnosed double round of mild Covid. Resaerch seems to point to immune dysfunction in the olfactory epithelia and neuronal loss post-Covid-19 as a cause of smell loss:
https://www.science.org/doi/full/10.1126/scitranslmed.add0484?rfr_dat=cr_pub++0pubmed&url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org
Parosmia actually may be a regenerative sign, though it may require a long recovery time:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9731923/
Could it be that autoimmune disorders make one more susceptible to smell loss?
That seems to be a reasonable question, as SLE, RA & Sjogren’s may independently be able to affect olfactory function:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9955947/#:~:text=Interactions%20between%20the%20olfactory%20process,common%20in%20Omicron%2Dinfected%20patients.
I would be interested in hearing how others have fared with smell retraining. 👃